Allison 1000 Converters: The Next Generation (#6)

The turbine is the same for both the fifth and sixth generations. There is a minor difference in the turbine hubs. The cross section of the turbine hub from the thrust washer surface on the cover side to the bearing surface on the stator side is the same on both fifth and sixth generations. The 2006- 2007 turbine hubs have a machined groove that is used to retain the enclosed bearing (Figure 4). The inner race (AL-HR-2) of the enclosed bearing is designed to fit into the retaining groove of the turbine hub. This groove was eliminated in the 2008 model when the enclosed bearing was replaced with an open bearing. If you are using a 2006-2007 fifth generation bearing on a 2008 turbine hub, you may consider machining a groove into the hub so that stress is not put on the inner race of the enclosed bearing.

The stator and corresponding bearings and shims are where you will find the biggest differences between the two generations. The impeller side bearings both have the same 2.650" I.D. and both rest against a .030" thick shim with three internal tangs. Both bearings are enclosed, and the only way to tell them apart is by measuring the thickness. The 2006-2007 bearing is .220" thick and the 2008 bearing is .250" thick. The turbine side bearings are easier to identify. The 2008 uses a .188" thick open bearing, and the 2006- 2007 uses a .220" thick enclosed bearing. The turbine side bearing shims are also different. The 2008 is .045" thick and the 2006-2007 is .030" thick. The stators are also different to compensate for the difference in bearing thicknesses. The recess for the impeller side bearing is .040" deep on the 2008 stators and only .010" deep on the 2006-2007 stators. The depth of the recess is the best method for identifying the stators (Figure 5).

Allison 1000 Fifth and Sixth Generations Interchange Rules

1. The impellers and piston/damper assemblies will interchange without modification.

2. The covers will interchange if used with the correct thrust washer (end play issues or possible thrust washer breakage can result if mismatched).

3. The 2006-2007 5th generation turbine assembly can be used with either the 5th or 6th generation stator assemblies. If a 2006- 2007 stator assembly is used with a 2008 turbine hub, a retaining grove should be machined into the turbine hub to prevent the bearing race from cracking.

4. The stators, with corresponding bearings and shims, may be interchanged if kept as a matched set. Mix-matching any one of these parts will cause a lot of grief.

Also remember that there are two different impellers and three different stators. They must be matched correctly to get the proper stall torque ratio and K factor.

Ed Lee is a Sonnax Technical Specialist who writes on issues of interest to torque converter rebuilders. Sonnax supports the Torque Converter Rebuilders Association.